Isolation and characterization of a phospholipase B from venom of Collett's snake, Pseudechis colletti

Phospholipase B in the venom of the Australian elapid snake, Pseudechis colletti, was purified to near homogeneity. By means of gel filtration it had an Mr of about 35,000, and by SDS-polyacrylamide gel electrophoresis an Mr of about 16,500. These presumably are dimeric and monomeric forms of the enzyme. It was isoelectric at pH 6.2 as compared to 7.8 for phospholipase A2 from which it was readily separated. It was relatively thermostable. As determined by release of water-soluble phosphorous, it degraded phosphatidylcholine and phosphatidylethanolamine, but did not degrade other phospholipids tested. The purified enzyme was strongly hemolytic in vitro for rabbit and human erythrocytes, but not for bovine or ovine erythrocytes. Hemolysis of rabbit erythrocytes gave rise to membranes showing ultrastructural changes that may be unique for this enzyme. The protein was highly active in producing turbidity in dilute solutions of egg yolk. It was cytotoxic for cultured rhabdomyosarcoma cells and was lethal for mice in which death was preceded by massive myoglobinuria.